Recutting Sapphire

[chrono]

I have had very good success with a few native cut stones; a Russian cut pink spinel, Tanzanian cut tsavorite and spinel, and I have no idea who cut the remainder of my red spinels. All are native cut (deeper pavilion and some have a slightly lower crown that I prefer) but no windowing, lopsidedness and the culet is centered to the naked eye. Generally quite pleasant to the eye. Of course, none are eBay stones. That is one shark infested water I refuse to thread in. I do not love them any more or less than my precision cut spessartite, spinels, zircon and tourmalines. Each has their own “character”.

 

[LD]

I agree Chrono. I think native cut stones and precision cut stones both have a place in our coloured world! I adore a precision cut gem but very occasionally they can be cut so well that they almost look like a synthetic gemstone - sacrilege to say I know. On the other hand, with a native cut gemstone there''s little chance of that and so the looks is more organic and natural looking.

 

[colormyworld]

Very interesting thread here. I think most know where I am on the issue.

Gene if your precision cut stones should some how become damaged, nothing major say a small chip on the pavillion or crown. How much weight loss would one expect for a repair?

 

[PrecisionGem]

Colormyworld, thats hard to answer with out looking at the stone.

Chrono, your Tanzanian cut Tsavorite, was precision cut by a master German cutter, working for Eric in Tanzania. I wouldn''t consider that to be a typical "native cut" stone.

 

[Michael_E]

Date: 7/31/2009 1:00:50 PM
Author: LovingDiamonds
Chrono/TL - The dimensions of the above stone are 11.00 x 9.00 x 6.00 so not particularly deep or shallow I don''t think. I''m prepared to lose carat weight to make this more beautiful (it deserves it)!

Let''s see that''s 66% depth right now and if the crown isn''t too tall it would be a perfect candidate for a re-cut. It probably has a significant belly which can be trimmed to give good enough angles on the pavilion to remove the window entirely. In this sort of re-cut, where you are concerned about weight loss, you won''t be maximizing anything, just removing the window. Still the increased brightness of the stone will most likely make the color a little less intense and the stone much brighter.

This thread is interesting, but one thought hasn''t popped up much yet and that is the cost and availability issue. There really is very little nice sapphire rough floating around out there for sale. This makes the choices for cutters and end consumers alike, very limited as far as getting precision cut sapphires in sizes over about 2 carats. The cost also becomes quite a sticking point when the better stones cost $1500 per carat and up. Not many people have the guts to turn a $5000 stone over to their favorite cutter to let them work it over. The basic choice generally comes down to getting a well done native cut in a fantastic color or getting a similar stone re-cut and reaching down deep into your storehouse of courage to let someone grind off expensive material hoping that it turns out enough better than the original cut to make it worth doing.

 

[megeve]

Date: 7/31/2009 4:43:33 PM
Author: PrecisionGem
Colormyworld, thats hard to answer with out looking at the stone.

Chrono, your Tanzanian cut Tsavorite, was precision cut by a master German cutter, working for Eric in Tanzania. I wouldn''t consider that to be a typical ''native cut'' stone.

Thats good to know, Gene! Thanks for the info!

Its a pity that Eric is not making it a known fact!

 

[chrono]

Date: 7/31/2009 4:43:33 PM
Author: PrecisionGem
Colormyworld, thats hard to answer with out looking at the stone.

Chrono, your Tanzanian cut Tsavorite, was precision cut by a master German cutter, working for Eric in Tanzania. I wouldn''t consider that to be a typical ''native cut'' stone.

Gene,
I had no idea. Eric needs to sing the praises of his cutter a little more loudly.

 

[PrecisionGem]

Not all his stones are cut by this guy, but the more important ones are. He does good work, we had the pleasure of meeting him a few times while in Africa.
So, since your tsavorite is precision cut, does that mean the color isn''t that good?

 

[PrecisionGem]

If fact while we were in Mark Saul''s office, his cutter came in to pick up a native cut stone, that Eric wanted re-cut to improve color and make. Rodger, Peter and I, along with the German cutter went over some options to improve this stone. Apparently the Saul''s haven''t realized that recuttig hurts the color and causes zoining of a stone yet either.

 

[chrono]

Gene,
Do you know if Eric’s master cutter also uses software simulations and the like? I know he cut a stone for me that was very pretty in the rough but after cutting, the colour was not as vivid and neon as expected. It is still a nice looking stone but the colour was not “wow” as expected. Hence, just because it is precision cut does not guarantee a great end result.

 

[PrecisionGem]

I don''t know if he does use a program to create his designs or not.

Did you see the stone in person before it was cut, or only from a picture. I''m thinking that a lot of this discussion has to do with how a stone looks in a picture, rather than in person.

 

[chrono]

I never saw the stone in person or a picture before it was cut. All I know is that Eric picked the rough based on the requirements I gave him. I think he was also disappointed that the colour did not turn out well after cutting.

 

[Gailey]

Date: 7/30/2009 11:08:19 AM
Author: LovingDiamonds
From a consumer''s point of view .......... this is a Paraiba Tourmaline that I bought - fully aware of the hideous window. I did think I could live with it. I can''t. I''m pretty convinced that re-cutting would enhance the colour and return to the centre of the gemstone. Could I live with a smaller gemstone? Yes because it''s just sitting in a box and will never be worn otherwise! Will I take the risk of a re-cut? Yes because again, it will only sit in a box otherwise! What use is that?!

I''m getting a strong sense of Déjà vu about this, so maybe I''ve offered this suggestion to you before LD, but consider contacting Tony Lloyd-Rees about your stone. He does restoration cutting and re-cuts as his core business I believe. He did an amazing job for a damaged emerald belonging to a friend.

 

[T L]

Okay, I''m really confused as to how this "optimzer" software works. Unless it takes into account RI, tone and saturation along all axis'', how do you know you''re getting the best cut from a stone to get the best color and light return? You could cut a stone with the fanciest cut in the universe, and it could still go extinct on you. I''ve seen that happen before. Just curious.

 

[PrecisionGem]

Date: 8/3/2009 4:11:07 PM
Author: Chrono
I never saw the stone in person or a picture before it was cut. All I know is that Eric picked the rough based on the requirements I gave him. I think he was also disappointed that the colour did not turn out well after cutting.

I guess at this point, you should stay away from well cut stones, and keep to native cuts with windows. It seems it''s the general view on this thread that native cuts are better.

 

[colormyworld]

Perhaps Chrono is really just tired of people trying to tell her what they should like. I know I am. Or perhaps the steady droning on about how all "native" cut stones are just cut for weight and face up size only with no thought about how the stone will look when finished. ect. ect. ect. Please just give it a rest !!!.

 

[T L]

Date: 8/3/2009 6:59:16 PM
Author: PrecisionGem

Date: 8/3/2009 4:11:07 PM
Author: Chrono
I never saw the stone in person or a picture before it was cut. All I know is that Eric picked the rough based on the requirements I gave him. I think he was also disappointed that the colour did not turn out well after cutting.

I guess at this point, you should stay away from well cut stones, and keep to native cuts with windows. It seems it''s the general view on this thread that native cuts are better.

Gene,
You seem to be taking this personally by those comments. I don''t think Chrono ever said she prefers all native cuts with windows over precision cuts. Actually she did say in an earlier post in this thread, that if all things were equal, she would prefer a precision cut over a native cut. I said the same thing as well.

However, I think the point that some of us are trying to make is that people shoudn''t just go and recut a native cut and expect a dramatic and better difference, like a fine plastic surgeon would perform on a patient. I don''t care for windows in gems at all, but I will put up with a window, if the color is amazing, like LD''s cuprian (BTW LD, if you don''t want your cuprian, I''ll take it

). I much rather have LD''s cuprian, window included, than an overly extinct precision cut gem for example.

However, if LD''s cuprian were to be recut in a fine precision cut by someone like you

, and the recut didn''t ruin the stone''s color, I think it would be beyond stunning.

It''s just a risk you take with a fine stone like that I guess, and why I warn against some recuts.

 

[PrecisionGem]

I wouldn''t consider an "overly extinct" cut to be a precision cut. I maybe wrong, but your words make it sound that you think a "precision cut" would "ruin the stone''s color", make it "overly extinct", or cause color zoning. Every is entitled to their opinions, I just happen to disagree. I''m not trying to tell anyone what they should like. I simply made the statement that a stone can be recut and it can be made more beautiful, and I have never said that all native cuts are poorly cut.

As far as the software I use goes, it does take into account the RI and other optical properties of the stone.

I don''t do recuts for people, nor do I recommend people buy a stone with the plan to have it recut. But I do know, there are a lot of stones every year professionally recut, by professionals, for members of the trade that are then sold for a lot more than they would have before they were recut. This is just a fact. You many not thing the stones look better, that''s you opinion, but the fact is they are recut to increase the value, not decrease it.

 

[Michael_E]

Date: 8/3/2009 6:56:37 PM

Author: tourmaline_lover
Okay, I'm really confused as to how this 'optimzer' software works. Unless it takes into account RI, tone and saturation along all axis', how do you know you're getting the best cut from a stone to get the best color and light return?

The "optimizer" software can only optimize one thing at a time and it only gives a person feedback in numbers or visually showing what a stone will look like when cut at different angles and shapes and under specific lighting conditions. Things like brightness, scintillation and color saturation are all trade offs with each other to some extent and the software can't optimize for personal preference. There are still variables which must be combined through experience to arrive at the best combination of properties for any given gem. I use two very different programs and the most realistic is one called Maxwell Render. It's used mostly by architects and uses optically correct ray tracing calculations to show what a stone will look like after it's been cut. The problem is that this program also makes clear the importance of different backgrounds, lighting patterns and even how close you are to the stone and makes it obvious that there is no "perfect" cut. It shows that some cuts are better for different situations and personal preferences, so it's still a bit of a guessing game when deciding how to cut a stone.

You could cut a stone with the fanciest cut in the universe, and it could still go extinct on you.

Well then THEY aren't using the right software !

Extinction is caused by a few things that are often beyond a cutters control. Things like "head shadow" however can be overcome with the appropriate cut style...as long as your head is far enough away from the stone. Other things like dark body colors make this a more difficult problem, BUT the software does make it an easier problem to solve. For instance, many people have the mistaken impression that making a dark stone more shallow will brighten it, since it makes the light path shorter. The reality is that dark stones must have their angles maximized for brightness, which often means that they should be cut deeper.

Concave cut stones have traditionally been very hard to design, but with this rendering software I can show how they will look before wasting any material cutting them. I don't cut them yet by the way, just messing around with how they'll look. Here's a rendered concave cut round in aquamarine.

 

[Michael_E]

Since this thread is about sapphires I thought that I''d add a neat render of an Asscher cut sapphire and a standard round brilliant cut aqua. Kind of neat images I think.

 

[D&T]

Michael - slight thread jack - that concave rendering of that Aqua looks amazing! I totally will take one of those from you

 

[T L]

Michael,
Thanks for the informative post. The only thing I can't see the software doing properly is predicting the loss of saturation of color in a stone when it is cut down, but I could be wrong. Just speculating.

 

[zeolite]

I’ve been following this discussion with interest, and without comment until now.
So far we are referring to precision cut or native cuts.

Let me split native cuts into two groups. “Good” native cuts have the proper pavilion angles, especially near the culet, may have steeper angles near the girdle, no window, and crown angles somewhere near the correct angle for dispersion, and tables not too large or too small. These “good” native cut stones, such as the golden sapphire and the tanzanite in this thread:

https://www.pricescope.com/community/threads/flower-gem-pics.121633/

still may lack precision facet placement, and at best medium polish, but they are quite acceptable as a finished gemstone. Perhaps 10% of native stones fall into this category.

The other 90% are the miserable excuse of cutting that Gene refers to. I totally agree with Gene that bad native cut stones are cut by cutters trying only to retain weight, with no consideration for brilliance, color or beauty. The cutters don’t have gemological training, or good equipment, and they rush the work, such that good polish is impossible.

I think LD’s Paraiba is well worth re-cutting, and would improve. It is my experience that it is an exceedingly rare stone that wouldn’t improve with re-cutting, and I am even referring to some supposedly well cut American stones. Let me give two personal examples:

I bought a dark blue emerald cut tourmaline of acceptable native cut and showed it to an AGTA multiple Cutting Edge winner for re-cutting. That very experienced cutter said it wouldn’t improve. Then and now I quite respect that person’s experience and ability. I kept it for about two years more, and then decided it was going to be recut, I’m not happy with it. It was recut to an opposed bar, and is now my single finest color blue tourmaline (and I have about 10 of them). It positively came alive after the re-cutting!

I bought a quite well cut pastel yellow grossular garnet in a brilliant cut, apparently cut quite well by an American cutter. The gem was pretty good, except that I happen to own 8 superbly cut yellow grossulars. A well cut and polished Tanzanian yellow grossular can even make a yellow diamond beg for mercy! I took my grossulars to Tiffany’s (Rodeo Drive) and with a side by side comparison, two salespeople agreed. They had never seen a grossular garnet at that level of performance!

The original stone was cut above the critical angle, and no window, and had a better than average polish. The stone was recut, changing the pavilion angle by two degrees, the crown angle about the same, and given a superb polish. The re-cut stone absolutely came alive. I could not believe how much it improved, with so little adjustment! I knew what it should have been, based on my other yellow grossulars, and now it was a match for any of them!

But a gem owner, in requesting a recut, should find a cutter they trust, let him make all of the decisions, and accept whatever results. If you are afraid to take chances, you will miss out on what could be possible. There are going to be wins and losses along the way. But the wins make it worthwhile.

Well cut, take no prisoners, 1.05 ct pink sapphire:

 

[T L]

Date: 8/3/2009 9:24:33 PM
Author: PrecisionGem
I wouldn't consider an 'overly extinct' cut to be a precision cut. I maybe wrong, but your words make it sound that you think a 'precision cut' would 'ruin the stone's color', make it 'overly extinct', or cause color zoning. Every is entitled to their opinions, I just happen to disagree. I'm not trying to tell anyone what they should like. I simply made the statement that a stone can be recut and it can be made more beautiful, and I have never said that all native cuts are poorly cut.

As far as the software I use goes, it does take into account the RI and other optical properties of the stone.

I don't do recuts for people, nor do I recommend people buy a stone with the plan to have it recut. But I do know, there are a lot of stones every year professionally recut, by professionals, for members of the trade that are then sold for a lot more than they would have before they were recut. This is just a fact. You many not thing the stones look better, that's you opinion, but the fact is they are recut to increase the value, not decrease it.

No, not at all. I think you are misreading what I'm saying (the problem with conveying information through the written word I guess

). In fact, I think a cut, any type of cut, precision or native, has the ability to make a stone go extinct if it is not cut properly. Some material will be extinct no matter what, but some have the ability to be brighter through certain types of cutting. You yourself once told me that darker garnets, as in the red family of garnets, often fare well with larger facets, especially checkerboard cutting on the table, and that smaller facets can cause extinction. In other words, if a red garnet is cut with a precision cut, but with smaller facets, it might not bring out that stone's best potential.

ETA: I love my precision cut stones, and when cut well, and with great color to boot, they're just perfection to me. I have a few native cut stones I would never recut though. Again, as Michael stated, I would be worried that the wrong optimizer software would be used, or no software when redesigning the stone. I think that people considering a recut should probably use a cutter that has access to this software.

 

[serenitydiamonds]

Date: 7/30/2009 3:27:39 PM
Author: Chrono
I am afraid I have to agree with TL on this one too. I’d rather take a poorly cut stone with great vivid colour over a precision cut stone with poor colour.

I agree with you too Chrono, and the Native cutters know this. The cutters in Colombia know quite a bit about their audience (I was shown a Japan color preference parcel, a US prefer color parcel, etc). The cost of a bag of top color Emeralds trumps the low color ones every time I go. Same is true for Sapphires from Burma and Thailand. The cutters know exactly how to cut top color and top weight to get top dollar.

The only thing noticed across the room for gems is color.

--Joshua

 

[chrono]

I have two gorgeous cobalt blue spinels that look to be quite good native cuts or if I am incorrect, then they may have been cut by very good cutters who tried to preserve weight, size, colour, etc (the entire package). One has a very deep belly and slightly off centered keel style culet. The other has a slightly skewed table. To me, these are minor and I would never have them recut. I don’t think the improvement (if any) will outweigh the loss of weight incurred, and conversely decrease the value of the stone. Both are about 2 carats thereabouts.

 

[chrono]

Zeolite,
So you brought your dark blue emerald cut tourmaline to another expert precision cutter for a recut? Was there a lot of material loss? I''m just curious, that''s all. I am too afraid to take risks, especially in something that is very expensive and difficult to find in the first place.

 

[PrecisionGem]

Date: 8/3/2009 10:37:38 PM
Author: serenitydiamonds

Date: 7/30/2009 3:27:39 PM

Author: Chrono

I am afraid I have to agree with TL on this one too. I’d rather take a poorly cut stone with great vivid colour over a precision cut stone with poor colour.

I don''t think the discussion here is (top color, poor cut), vs. (poor color precision cut), it''s; can a good cut improve a good color stone. My feeling is that it can. Apparently others feel that it can not, and that in fact a "precision cut" makes a stone loose color, emphasize zoning and cause extinction.

 

[zeolite]

Date: 8/4/2009 8:57:03 AM
Author: Chrono
Zeolite,
So you brought your dark blue emerald cut tourmaline to another expert precision cutter for a recut? Was there a lot of material loss? I''m just curious, that''s all. I am too afraid to take risks, especially in something that is very expensive and difficult to find in the first place.

The tourmaline went from 6.54 cts emerald cut to 4.56 cts opposed bar cut, a considerable weight loss. But the face up size didn''t change at all. Only the height was reduced. It immensely improved the overall value, even considering the weight loss, since the original emerald cut was too dark to be attractive.

I made the gamble that it would improve, I made the choice of how to re-cut it to improve it, and I did the re-cut. I had only been cutting about 8 months, and had not won any Cutting Edge awards at that time.

 

[Michael_E]

Date: 8/4/2009 10:00:56 AM
Author: PrecisionGem

I don''t think the discussion here is (top color, poor cut), vs. (poor color precision cut), it''s; can a good cut improve a good color stone. My feeling is that it can. Apparently others feel that it can not, and that in fact a ''precision cut'' makes a stone loose color, emphasize zoning and cause extinction.

This is too simplified Gene. I think that a good cut will improve a stone 95% of the time. 1% of the time it will lighten a stone which may already be acceptable, though not great and 4% of the time it''s just not worth the expense, since the stone may already be nice enough and a re-cut may cause too much weight loss for a subtle improvement. As for zoning and extinction, my view is that a well thought out and executed re-cut will always improve these properties of a gem. "Well thought out and executed" is the key here as this takes time and a person needs to find someone willing to put that time and thought into their re-cut.